The present invention relates to a device for supplying power to an electronic computer in a motor vehicle, having two voltage regulators which are operable independently of one another and act in parallel at both their inputs and outputs, and in which the desired output voltage is regulated downwards from the input voltage, with the first regulator being embodied as a linear regulator and the second regulator as a switched-mode regulator.
Multifarious task definitions in the control technology of motor vehicles increasingly demand the use of computers for measurement, control and recording purposes. Also, the operation of personal computers in the motor vehicle is to be made easier for passengers. Such instruments urgently require an uninterrupted power supply which shields such items of equipment reliably from dips in vehicle network voltage, for example during starting of the internal combustion engine, or from voltage peaks in the event of load dumping. Appropriate solutions to these problems have so far provided relatively large-volume circuits, which have also comprised, inter alia, a booster battery for ensuring a stored energy time during starting. The costs of these devices have been correspondingly high, and they have, moreover, not been maintenance-free in the case of the use of a booster battery.
German Patent Document 3,837,071 discloses a power supply system in which at least two power packs are connected in parallel on the output side in order to feed a common load. In this arrangement, the output power of the respective power pack is regulated by its temperature.
Related solutions were described in the specialist journal Electronic Design 14, Nov. 1985, pages 125 to 132. These solutions are intended to create a reliable possibility of operation up to the thermal overload limit of each individual module of a multiplicity of power supply modules acting in parallel.
An object of the present invention is to provide a device for supplying power to an electronic computer in a motor vehicle, which guarantees a proper power supply within a very wide input voltage range and without the use of booster batteries, and in addition protects connected loads against overvoltages.
This and other objects are achieved by the present invention which provides a device for supplying power to an electronic computer in a motor vehicle and has first and second voltage regulators, operable independently of one another and having parallel inputs and outputs, and in which a desired output voltage is regulated downwards from an input voltage provided by a vehicle network. The first and second regulators each include at least one capacitive storage means at their inputs. A protective device is coupled to the inputs of the first and second regulators, this protective device including means for connecting and disconnecting the first and second regulators from the input voltage. A voltage monitoring circuit is coupled to the first and second regulators and the protective device. The voltage monitoring circuit detects and evaluates the input voltage to be regulated downward from the vehicle network and includes at least one output each for individually controlling activation, voltage range by voltage range, of the first and second regulators and the protective device. The voltage monitoring circuit includes means for controlling, as a function of an evaluation result of the input voltage to be regulated downwards: no activation of the first and second regulators in an input voltage range from zero up to a first limit; activation of the first regulator in the input voltage range exclusively between the first and a second limit; activation of the second regulator in the input voltage range exclusively between a third and a fourth limit, the third limit being below and the fourth limit above the second limit; and activation of the protective device above the fourth limit for disconnecting the first and second regulators from the input voltage to be regulated downwards. In an embodiment of the invention, the first regulator is a linear regulator and the second regulator is a switched-mode regulator.
The present invention has the advantage of enabling a computer in a motor vehicle to have a reliable continuous supply in a wide range of fluctuation of the vehicle network voltage between approximately 40% and 300% of its nominal value, in a cost-effective way, with good efficiency and without the need for a separate booster battery. The invention also advantageously permits simple checking interrogation of the individual components and their correct functioning.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.